Penetration resistance of gypsiferous horizons |
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Authors: | R M POCH H VERPLANCKE |
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Institution: | Departament de Medi Ambient i Ciències del Sòl, Universitat de Lleida, Av. Alcalde Rovira Roure 177, 25198 Lleida, Spain;Department of Soil Management and Soil Care, Universiteit Gent, Coupure Links 653, 9000 Gent, Belgium |
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Abstract: | To assess the importance and the possible causes of penetration resistance of horizons with gypsum, 20 horizons in seven irrigated profiles were studied. Gypsum contents ranged from 0 to 900 g kg?1. Penetrometer tests were performed on undisturbed soil cores by means of a needle penetrometer at different matric potentials. The increase of penetration resistance on drying was caused by changes in the effective stress of the soils, calculated from their soil water characteristic curves. Multiple regression tests showed that besides water content and bulk density, gypsum content was positively correlated with penetration resistance. It seems that in the soils studied the increase of penetration resistance caused by gypsum is due to the growth of gypsum crystals in pre-existing pores, which reduces the volume of regular and continuous voids necessary for root growth. |
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